Receivers for television signals

ABSTRACT

A receiver is configured to receive television signals in a plurality of channels, a channel set identity, and a channel subset identity. Each channel defines a television program and/or other services provided by a broadcaster for the channel. The receiver is configured to store a reference channel set identity and one or more reference channel subset identities, compare the channel identity and channel subset identity for a channel in a received signal with the reference channel and channel subset identities, and output the received television signal for display of the program or other services defined thereby depending on the comparison.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 09/719,389, filed Jun. 25, 2001, which in turn is a nationalstage filing under 35 U.S.C. §371 of International Application No.PCT/GB99/01873, filed Jun. 14, 1999, and claims priority under 35 U.S.C.§119 to Great Britain patent application No. 9812797.0, filed Jun. 12,1998. Each application is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to improvements in receivers for televisionsignals.

BACKGROUND OF THE INVENTION

At present most television broadcasting, regardless of medium over whichthe signal is broadcast (Terrestrial, Cable, Satellite), is analoguebased and comprises a single television service (e. g. SKY ONE, SKYSPORTS, SKY MOVIES) transmitted on a carrier signal or channel. However,the use of digital based broadcast technology is imminent. Digitalbroadcast technology will enable television service companies totransmit in a single channel high definition television programmes, orplural programmes at conventional definition or multiple customerservices, or a combination of these.

In a conventional analogue-based television broadcast system programmes(or “services”) are broadcast by separate television service companieson a single carrier signal (“channel”). In a digital based broadcastsystem it is possible to broadcast plural services multiplexed togetheron a single carrier. Unless the context requires otherwise the term“channel” will be used herein to refer to the bandwidth used by a singleservice to broadcast television programmes or other customer services.The term “channel” therefore encompasses both an entire carrier signal(when the signal is used entirely by a single service) and a portion ofa carrier signal (when the signal is shared by plural services).

The ability to transmit multiple channels in a single carrier signalenables a far greater number of services to be provided in the digitaldomain than is possible in the analogue domain. Some of the channels ina carrier may be used to provide conventional television programmeswhile simultaneously other channels in the carrier are used to providedata for other customer services such as television programme listings,on-line programme ordering or so-called pay-per-view (PPV) services, andso on. Customer services should not be confused with the “services”provided by television companies as discussed hereinabove.

In our International (PCT) patent application published as WO 96/37996,the teachings of which are incorporated herein by reference, there isdisclosed a receiver for television signals, which receiver is arrangedto receive video signals comprising video data, information data andaudio signals comprising audio data and information data. The receiveris arranged to respond to viewer operation of a control device. Thereceiver includes a processor for processing selected information datato convert the same into signals representative thereof for output to atelevision in combination with the video signals. In one mode ofoperation the decoder responds to manipulation of the control device bycausing brief scheduling information pertaining to programmes of aplurality of different TV signals to be displayed over the receivedsignal. In another mode of operation the receiver is arranged to displaydetailed scheduling information pertaining to plural differenttelevision signals. The receiver is operable to receive signalscontaining video data representing a plurality of video clips. Theprocessor is arranged to process the signals and to cause simultaneousdisplay of the clips on a television screen. The processor is arrangedto respond to user manipulation of the control device by storing datafor subsequent viewing of user selected programmes. The decoder mayfurther comprise a modem and various types of digital storage mediaincluding Hard Disk, CD-ROM drive, Digital Video Disk.

In addition to such television related services some of the channels ina carrier may be used to provide on-line shopping facilities by which acustomer may purchase goods and/or services from their own home. Suchon-line shopping is, of course, only possible if there is an element ofinteraction between the goods/service provider and the customer.

The term “interactive services” will be used herein to refer generallyto on-line shopping facilities and the like made available via one ormore channels in a digital based broadcast system.

Digital data multiplexing techniques enable a single channel to carrysimultaneously multiple interactive services. In itself this creates aproblem. Many customers will find bewildering the large number ofinteractive services available to them. If customers become confusedthey will not make use of the interactive services. Clearly, this isundesirable.

Transmission bandwidth is a finite resource and will remain at a premiumeven if full advantage is taken of digital data compression techniques.This presents a problem when it comes to providing an interactiveservice. On the one hand it is desirable to present high qualitypictures and graphics. However, higher quality necessitates the use of alarger bandwidth. On the other hand it is desirable to keep costs downbecause customers will not make use of interactive services if they aresignificantly more expensive than comparable high street services.

In our International (PCT) patent application published as WO 97/23997,the teachings of which are incorporated herein by reference, there isdisclosed a receiver for television signals, which receiver is arrangedto receive video signals comprising video data and information data. Thereceiver is arranged to respond to viewer operation of a control device.The receiver includes a processor for processing selected informationdata to convert the same into signals representative thereof for outputto a television in combination with the video signals. The receiver isarranged to respond to the information data to output for display dataderived from said image data and said information data and representingan inter-active image. The receiver is responsive to viewer manipulationof the control device to vary the inter-active image and to establish atelecommunications link to a remote site for on-line interaction via theinter-active image between the viewer and the remote site. Theinteractive image may form part of an interactive services interfacecomprising a broadcast entry level and plural broadcast interactivelevels. The inter-active services interface may comprise one or moreon-line interactive levels entered from one of the broadcast interactivelevels for establishing an on-line connection with a remote site.

SUMMARY OF THE INVENTION

The present invention aims to facilitate the functionality and limit thebandwidth used for the transmission of schedule data in the decoder andEPG described in the aforementioned patent applications.

In one aspect the invention provides a receiver for receiving televisionsignals in a plurality of channels each defining a television programmeand at least a signal in one of the channels comprising or furthercomprising compressed data defining broadcast events in the channelsfrom time to time, the receiver being arranged to produce output signalsdefining an image of events in the programme schedule for displaying ona television screen and comprising means for receiving data defining adictionary representing text portions means for decoding the programmescheduling data to identify text portions in the dictionary, and meansfor constructing the image of events using the identified text portions.

In another aspect the invention provides a receiver for receivingtelevision signals in a plurality of channels each defining a televisionprogramme and/or other services provided by a broadcaster, and a bouquetidentity and a sub-bouquet identity for the channel, the receivercomprising means for storing a reference bouquet identity and one ormore reference sub-bouquet identities, means for comparing the bouquetidentity and sub-bouquet identity for a channel in a received signalwith the reference bouquet and sub-bouquet identities and means foroutputting the received television signal for display of the programmeor other services defined thereby depending on the comparison.

The ordering of the programmes or other services defined may also dependon the comparison.

In a further aspect the invention provides a receiver for receivingtelevision signals in a plurality of channels each defining a televisionprogramme and wherein the signals further comprise sorting data defininga sorting list and scheduling data defining a schedule of programmeevents, the receiver being arranged to filter the scheduling datadepending on the sorting data to produce output signals defining animage of selected events in the programme schedule for display as afiltered schedule on a television screen depending on the sorting data.

The invention also provides a receiver for receiving television signalsin a first plurality of channels broadcast in a first broadcast networkand a second plurality of channels broadcast in a second broadcastnetwork, the receiver comprising a cache store for storing programmeschedule data transmitted from time to time in at least one of thechannels broadcast in the first network, means for decoding the data inthe cache store for display of a programme schedule of the firstbroadcast network, and means for receiving and decoding programmeschedule data transmitted substantially continuously in at least one ofthe channels broadcast in the second network.

The invention provides a receiver for receiving television signals for aplurality of channels which together provide a time-shifted service, thetelevision signals comprising unique identity data for each channel andprogramme schedule data for a reference channel, the receiver comprisingmeans for determining from the data for the reference channel a schedulefor each other channel and means for displaying a schedule of programmesfor each independently identified channel in the time shifted service.

The invention provides a receiver for receiving television signals in aplurality of channels each defining a television programme and at leasta signal in one of the channels further comprising programme schedulingdata including pay-per view-events, the receiver being arranged tofilter the data pertaining to the pay-per-view events to produce outputsignals defining an image of a schedule of the pay-per-view events fordisplay on a television screen.

The above and further features of the invention are set forth withparticularity in the appended claims and together with advantagesthereof will become clearer from consideration of the following detaileddescription of an exemplary embodiment of the invention given withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a television receiver system;

FIG. 2 is a functional block diagram of a satellite decoder;

FIG. 3 is a functional diagram showing interaction between hardware andsoftware of the decoder of FIG. 2;

FIG. 4 is a schematic diagram representing a compressed text string;

FIG. 5 is a schematic diagram of a bouquet and a plurality ofsub-bouquets;

FIG. 6 is a stylized example of a Box Office menu; and

FIG. 7 is a stylized example of a Box Office screen.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

System Overview

Referring now to FIG. 1 of the accompanying drawings a televisionreceiver system 1 comprises a television (TV) 2, a digital integratedreceiver decoder 3 (decoder) connected to receive signals from asatellite dish antenna 4, and a video cassette recorder 5 (VCR), and amodem 7. The system 1 optionally further comprises a personal computer 6(PC) and a games console 8 each connected via respective lines to thedecoder 3. SCART connectors or other standard connectors may be used asappropriate. The decoder 3 acts as an interface between the TV 2 and theVCR 5, PC 6, modem 7 and games console 8 and thus serves to control thesystem 1.

Receiver/Decoder

FIG. 2 of the accompanying drawings shows the decoder 3 in greaterdetail. The dish antenna receives signals from a satellite (not shown).Signals from the dish antenna 4 are input to a tuner 12 and from thereto a quadrature phase shift key (QPSK) demodulator 13. Demodulatedsignals are error corrected by way of a forward error corrector circuit14. Satellite (and indeed cable) programmes are usually scrambled toprevent unauthorised access by non-authorised subscribers. The decoder 3therefore comprises a conditional access control circuit 16 whichco-operates with a smart card 16 a to determine whether the viewer hassubscribed to a particular channel and is therefore authorised to accessthe channel. Parental control over channel access is also provided, atleast in part, by the access control circuit 16. The decoder 3 furthercomprises a descrambling circuit 17 which is controlled by the accesscontrol circuit 16 to enable the descrambling of the signal byauthorised subscribers.

The received signals comprise digitally encoded data. It is envisagedthat the data will be compressed using for example the DVB/MPEG 2standards which permit both programme data and additional data (forexample interactive service data) to be transmitted in a single channel.DVB/MPEG 2 enables high compression ratios to be achieved.

Descrambled data is supplied to a transport/demultiplexor 15 whichseparates the data into video data, audio data, user services data,programme scheduling data etc. for distribution to various locationswithin the decoder. Demultiplexed signals are input to a videodecompression and processing circuit 18 utilising dedicated video RAM 17a, and an audio decompression and processing circuit 19, operatingaccording to the MPEG standard for example. Decompressed video signalsare input to a SCART interface 20 for direct input to the TV 2 and to aPAL encoder 21 where they are encoded into the PAL format for modulationby a UHF modulator 22 for output to the UHF input of the TV if sodesired.

The system 3 is controlled by a processor 23 which communicates with thevarious units of the system via a bus 24. The processor 23 hasassociated with it ROM 25 (optionally including a CD-ROM drive 25 a),RAM 26 (comprising both dynamic RAM and static RAM) and a flash(non-volatile and writable) memory 27. As will be explained in greaterdetail hereinafter the processor 23 controls operation of the decoder 3by controlling the tuner 12 to receive signals for the desired channelfrom the dish antenna 4 and to control demultiplexing, descrambling anddecompression so that the desired programme and/or interactive servicedata is displayed on the screen of the TV 2. Viewer selection of desiredprogrammes and customer services is controlled by way of a remotecontrol unit 28 which in response to viewer manipulation thereoftransmits control signals to a receiver 29 for input to the processor23.

The system 3 further comprises a high-speed data interface 30 and anRS232 interface 31 providing a serial link. The high-speed datainterface 30 and the RS232 interface may be connected to the PC 6 and/orthe games console 8 of FIG. 1 and/or other digital equipment (notshown). The high speed data interface 30 enables the system 3 to beconnected to other devices (not shown) for example to enable receptionof services transmitted via other media such as broadband cable anddigital terrestrial broadcast. The decoder 3 further comprises a modeminterface 32 for connecting to a telephone network.

Operation of the decoder 3, especially the processor 23, is controlledby software that makes the processor 23 responsive to control signalsfrom the remote control unit 28 and to data included in the signalreceived by the dish antenna 4 and in the memory units 25 to 27. Aschematic representation of the interaction between hardware andsoftware in the decoder 3 is shown in FIG. 3 of the accompanyingdrawings. The data in an incoming signal is separated by thetransport/demultiplexer 15 into video data and information data. Theinformation data is distributed around the hardware and software, aswill be described in greater detail hereinafter. The video data and theaudio data is demultiplexed and output in suitable form for supply to aTV by the MPEG video and audio circuits 18 and 19. When information isto be displayed either with or instead of the video, data representingthe information is output in suitable form for supply to the TV via anon-screen display (OSD) driver 33 and the video circuit 18. Signals fromthe OSD driver 33 and the video circuit 18 are combined as appropriatebefore being supplied to the TV. Operation of the software and hardwareof the decoder 3 is based around an operating system 35. The conditionalaccess controller 16 has associated software which interfaces with theoperating system. The processor 23 has its own base operating system 37which interfaces to the decoder operating system 35. Applications suchas an intelligent electronic programme guide (EPG) 39 and otherapplications 40 including interactive services interface to theoperating system 35 via an applications interface 41 and associatedapplication interpreter 42.

The software for conditional access applications such as the intelligentelectronic programme guide 39 are installed permanently withinnon-volatile memory, e. g. the ROM 25, of the decoder 3, but variableinformation such as new access codes and TV programme scheduling detailsis updated regularly via signals received from the dish antenna 4.Demodulated signals from the demodulator 13 are input to the transportdemultiplexer 15 which examines the data to decide where it should besent. From time to time significant changes may be made to conditionalaccess codes or to the manner in which the intelligent electronicprogramme guide (IEPG) 39 displays programme information. Also,programmes for additional applications, say an interactive shopping orbanking service for example, are also supplied via the satellite for thedecoder. Such application data is routed by the transporter 15 directlyto the appropriate areas 40 of the store.

Operating data 43 is supplied on a substantially continuous basis inevery channel. The operating data 43 includes conditional access data 44associated with a channel and/or programmes therein which enables theconditional access controller 16 to determine whether or not accessshould be allowed to a particular programme by descrambling the datatherefor. Additionally, operating data relating to interactive servicesis transmitted in dedicated interactive service channels which carrycontrol and information data for use by the hardware and software of theprocessor 23 and the associated memory devices 25 to 27. Thus, theoperating data 43 depicted in FIG. 3 also includes interactive serviceprograms and information 46 (for example relating to personal bankingservices) and indeed any other data 47 required on a substantiallycontinuous or regular basis for the aforementioned interactive services.

The transport/demultiplexer 15 is arranged to supply the operating data43 to the processor 23. The data is acted upon by the operating system35, the conditional access and/or other operating software. Theprocessor 23 responds to the data by sending appropriate commands orinformation to other units within the system. Control data is alsotransferred between the processor 23 and such units as the demultiplexer15, the video and audio decompressors 18,19, the remote control receiver29 and the high-speed data interface 30 via respective drivers 48 to 52.

The combined hardware and software of the decoder 3 enables the data inreceived channels to be decoded for display of viewer selectedprogrammes and customer services. The scrambling is controlled on acontinuous basis and the decoder can be updated with new descramblingcodes as and when required. Data for interactive services is suppliedand updated substantially continuously and programmes relating to newlyselected interactive services are downloaded into the decoder.

Operation of the decoder 3 in receiving and decoding data representingtelevision programmes and data defining scheduling and other informationrelated to the programmes is described in detail in our International(PCT) patent application published as WO 96/37996, aforementioned.Operation of the decoder 3 in providing interactive services isdescribed in our International (PCT) application published as WO97/23997, aforementioned.

Within the Digital Video Broadcasting (DVB) standards for digital TVtransmission there exists a standard for the transmission of scheduleinformation such that it can be decoded and presented correctly tosubscribers in the form of an Electronic Programme Guide (EPG).

This DVB standard is known generally as the SI standard and can be foundin the specification: ETS 300 468, ETSI Digital Broadcasting Systems forTelevision, Sound and Data Services; Specification for ServiceInformation (SI) in Digital Video Broadcasting (DVB) Systems 2ndedition. Guidelines for using the specification are given in ETSI ETR211-DVB SI Guidelines.

In order to allow broadcasters to utilise any proprietary features oftheir EPGs the SI standard includes a methodology for extending theformat of the service information (SI) stream by the inclusion ofprivate data tables and descriptors.

The above-described decoder 3 is, of course, designed to support themandatory parts of the SI specification. We have, however, extendedconsiderably certain aspects of the standard as is allowed by thestandard. The extended standard will be referred to herein as the XSIspecification. Among other things, the XSI includes the followingadditional features:

-   -   1. Compression, regionalisation, ordering and sorting techniques        which are used for bandwidth efficient transmission of data;    -   2. Organization and implementation of data caching;    -   3. Implementation of time-shifted services.

These additional features unique to the XSI specification, will bedescribed in detail in the following.

Compression

In order to save bandwidth on the transmission medium and memory in thereceiver text is compressed. A compression algorithm resident in thedecoder 3 uses “dictionaries” which are received from the transmissionmedium and held in memory, e. g. the RAM 26. The dictionaries may beregarded as look-up tables in which portions of text are stored againsttable addresses in the form of compressed text strings. Thus, instead oftransmitting full text over the transmission medium it is only necessaryto transmit the compressed text strings, thereby reducing the bandwidthrequirement for the transmission of text over the transmission medium.

An example of a compressed text string 60 is shown in FIG. 4 of theaccompanying drawings. The string 60 comprises a field 61 of two bitswhich identifies the version of the dictionary in which the relevanttext is held. The string also comprises a field 62 of indefinite lengthcontaining data pertaining to compressed text.

Two versions of the dictionary are normally transmitted and a furtherdictionary may be stored permanently (or for an extended period of time)in the memory of the decoder 3. The transmission of two versions of thedictionary enables the text compression to be optimised according to thedata currently being transmitted by allowing the dictionary to beupdated over time. Special promotions in one week may no longer beavailable in the next or may be replaced by another, different promotioncausing different dictionaries to be required for full efficiency. Thetransmission of two dictionaries reduces the amount of memory requiredto store a dictionary because at any given time only a single dictionaryneed be stored in the decoder 3. Typically the decoder 3 will bearranged to store in memory the most recently accessed dictionary, be itfor the present week or for the next week, and download the otherdictionary if necessary the next time data for the dictionary isbroadcast (typically every five seconds).

This approach minimises delay, at most, to ten seconds if data for therequired dictionary is not in the decoder's memory. It also minimisesbandwidth requirements because, instead of transmitting all text forevery page of the programme guide each time data for a page istransmitted, each text string is transmitted only one in thedictionaries and the data for each page is reduced to the compressedtext strings, such as the compressed text string 60 in FIG. 4. Onreceipt of data for a page the decoder uses the compressed text stringstherein to look up the complete text in the appropriate dictionary anduses the text from the dictionary to reconstruct the full text of thepage.

Several text fields are compressed including:

-   -   Extended service descriptions (including information about the        channel)    -   Names of each linked event (including the name or tile of a        programme)    -   Short event names    -   Extended event descriptions (including a brief synopsis of the        programme)    -   Special event messages (including discounts, say, for early        ordering on pay-per-view (PPV) services).

Regionalization

The DVB standard requires broadcasters to register with ETSI so-called“bouquet” identities. Channel line-up information is carried in aBouquet Association Table (BAT) which is an optional DVB standard table.

One way in which services could be regionalized would be to registerwith ETSI a different Bouquet ID for each region of interest, i. e. oneBouquet ID for England, one for Wales and one for Scotland for example.There are, however, only a limited number of Bouquet IDs available whichlimits the number of regions that may be defined for a given broadcastcompany. Another problem is that the number of BATs increases with thenumber of regions, thereby increasing bandwidth overheads.

In order to overcome this problem XSI introduces the notion ofsub-bouquets. Services are listed within sub-bouquets according to thecontents of sub-bouquet descriptors found within the BAT. FIG. 5 of theaccompanying drawings shows a bouquet 70 which is identified by abouquet ID and plural sub-bouquets 71 to 75 each identified by arespective sub-bouquet ID. This information is broadcast in a BAT. Oneof the sub-bouquets 71 may contain information identifying services thatare common to all regions, for example nationwide services such as SKY1,SKY2, BBC1. Other sub-bouquets contain information identifying servicesthat are specific to each region, for example the British ITV companies.

When a subscriber is first connected he or she provides information(such as a post code) which is used to transmit to the decoder relevantbouquet and sub-bouquet IDs to enable the subscriber to receive andstore the common services and regionalized services for his region. Eachdecoder will receive the bouquet ID together with the common sub-bouquetID and the specific region sub-bouquet ID for the location of thedecoder. A default may be set up to enable, say, a non-subscribingviewer to receive free services from within the common and/or specificregion sub-bouquets. The regional information may be prestored in theviewing card. It will be appreciated from the foregoing that such ascheme allows significant reduction in the bandwidth used in describingregional channel line-ups.

Ordering

Channels are defined in a predetermined order and are designated achannel number depending on that order. In order to enable the order inwhich channels appear in the EPC to be different than the channel numberorder, each sub-bouquet includes order numbers which are separate fromthe channel number.

All services are assigned a unique service key which is their identifierin XSI. Basically, the service key corresponds to the triplet (originalnetwork id, transport stream id, service id) which is the uniqueidentifier of a service as defined in ETSI, ETS 3000 468.

Services are given attributes which vary on a sub-bouquet basis. Theseattributes are used to inform the EPG application of the displaystrategy for the service. The attributes are:

-   -   Logical channel number (this is the “channel number” as seen by        the viewer).    -   Order number (this number is used to define the order in which        services appear in the EPG grid and listings).    -   Navigation and display indicators (four flags tell whether the        service is accessible in channel surf mode, in search & scan        mode where listings are displayed over TV viewing, whether the        service is to be displayed in the full listings screens and        whether it cannot be locked out by parental control).

Sorting

Data broadcast for the EPG includes true information such as the time atwhich broadcast of a programme is scheduled to start. It would, however,be desirable to be able to sort programmes in another order within theEPG, for example alphabetical order.

Index lists of sorted events by time or alphabetically are computed inthe head end, sent over the air as part of the XSI and cached in thedecoder 3. This saves computer power in the decoder because sortinglistings can be a very CPU intensive job. The sorted indices also conveyinformation such as genre/sub-genre, PPV post-buying window and othermarketing-oriented flags (PPV, Critic's Choice, New Show, Event) thatare used for filtering purposes and to support the Box Officefunctionality.

In addition to the above-described XSI, other improvements have beenmade to the EPG in the decoder 3. The improvements will be described inthe following.

Caching

A cache store 26 a (see FIG. 2) is provided in the decoder to enable EPGdata to be broadcast and built-up slowly over time, rather than beingbroadcast continuously. The cache store 26 a is a RAM device which maybe separate from or part of the RAM store 26. The cache store 26 a isshown separate from the RAM store 26 for the purpose of illustration inFIG. 2.

Data caching is also used by the decoder to enable the decoder to beused for a number of different broadcast networks. Typically, thedecoder will be required to be able to receive broadcasts from a digitalsatellite television network and a digital terrestrial televisionnetwork. Conceptually, a separate EPG is provided within the decoder foreach network. Thus, in the case where the decoder is required to receiveboth satellite and terrestrial broadcasts, the decoder may be regardedas providing both a satellite EPG and a terrestrial EPG.

The satellite EPG in the decoder is arranged to cache data as and whenrequired taking information from the EPG transponder of the satellitenetwork. Information on the EPG transponder is cycled at a hightransmission rate in order that the EPG performs with a reasonableresponse period.

The bandwidth available for delivery of data to the terrestrial EPG inthe digital terrestrial environment is considerably less than thatavailable in the satellite environment. Therefore, unlike in thesatellite environment, within the terrestrial environment it is notpossible to dedicate one multiplex to transmit the full seven dayschedule of EPG data at high speed.

Therefore in order to enable the full schedule of listings to bedisplayed with a reasonable response rate the full schedule is “trickle”transmitted on all terrestrial multiplexes and the terrestrial EPGstores the complete schedule in the cache memory. This is possible evenwith the smaller amount of memory available in the set top box becausethere are a small number of channels carried on the terrestrial network.

As shown in FIG. 2, the decoder is made able to tune to digitalterrestrial TV by the addition of terrestrial tuner 12 a to the highspeed port 30 of the set top box. (Similarly, a terrestrial set top boxwill be able to tune to digital satellite TV by the addition of asatellite tuner.) Ideally, in these cases the EPG resident in the settop box will be capable of seemlessly merging data from the twoenvironments.

An issue that because of memory limitations the combined network set topbox will not be capable of storing the entire satellite network schedulein its memory, neither would it be a good use of memory to store theentire terrestrial schedule when only part of the satellite schedule isavailable.

In order to solve these difficulties when a terrestrial only set top boxis upgraded to be capable of tuning to the satellite network then thecaching algorithm is changed to be that of a satellite set top box.Thus, the full schedule is no longer held in set top box memory butsections of the schedule are obtained as required from the fastcontinuous transmission on the EPG transponder of the satellite service.In order for this to work the schedule for the terrestrial listingsschedule must also be transmitted in the data transmitted on thesatellite EPG transponder.

With this design any satellite capable set top box (i. e. a satelliteonly system, a satellite system with a terrestrial “side-car”, or aterrestrial system with a satellite side-car) will obtain its schedulefrom the satellite EPG transponder on demand and only caches the pieceof the schedule currently in use. A terrestrial only set top box howeverwill have a different caching algorithm and caches the entire schedulefor the terrestrial transmission.

The caching strategy can be refined by sending new caching parametersover the air on a per platform basis. A platform is one type of hardwarefrom a certain manufacturer. This enables manufacturers to vary the costand performance of different models in their ranges by specifyingdifferent sizes of cache store for different models. The parametersindicate the schedule depth of the listings that are to be cached andmaintained in the decoder as well as the schedule depth of the sortingindexes. Thus models with larger cache stores will be able to store moreinformation allowing the owner to access the information more quickly.

Time-Shifted Services

Standard DVB SI allows time-shifted services to be defined. By way ofexample, time-shifted services include the broadcasting of a singlemovie in different channels at different start times. For example, asshown in FIG. 6, a movie may first be broadcast starting at 6:00pm on achannel 75, then broadcast of the same movie will start again on adifferent channel 76 at 6:30pm, then again at 7:00pm on channel 77 andso on. According to the standard DVB SI one of the channels, i. e.channel 75, is a reference channel with a reference schedule and allother channels 76,77 have schedules which are time-shifted versions ofthe reference schedule. That is, the other channels 76,77 only differfrom the reference channel 75 by the time-shift and cannot have achannel name of their own.

Our XSI provides greater flexibility by allowing each time-shiftedchannel to have a name which is different than that of the referencechannel.

Thus, for example, a reference channel called “Box Office” could havetime-shifted channels called “Box Office 1”, “Box Office 2”, “Box Office3”, etc.

The “Box Office”

As discussed within our aforementioned earlier applications, within theEPG there is a dedicated section for the display of Pay-Per-View (PPV)programmes. PPV events include both one-off PPV events and near video ondemand PPV events. This is the “Box Office” section of the EPG.

Although the PPV programmes are also listed in the TV Guide section ofthe EPG, Box Office has been created to encourage subscribers to browsePPV programming. The benefit of having a separate section that listsonly PPV events is that it will create a subscriber perception thatbecause all programming listed in this area incurs an extra charge itcontains only programmes of the highest value. This encourages thesubscriber to use this section of the EPG.

Whilst other EPGs list PPV programming within their normal listings(some allow subscribes to apply filters within the normal listings tofind the PPV events), as far as we can establish only the Sky EPG has anentire section dedicated to this purpose.

FIG. 6 of the accompanying drawings shows an example of a Box Officemenu 80. The Box Office menu items allow access to listings by Movies,Sport and other programming genres. For each of these genres programmescan be listed in start time order, e.g. “Movies” 81, “Sports” 82 or“Events” 83. Programmes can also be listed by alphabetic order by title,e. g. “Movies A-Z” 84, “Sports A-Z” 85 or “Events A-Z” 86. Listings ofnew PPV programmes of each genre are also available, e. g. “New Movies”87, “New Sports” 88 or “New Events” 89.

Another menu item “Free Previews” 90, when selected, tunes the set topbox to a PPV barker channel which continuously promotes PPV programming.

FIG. 7 of the accompanying drawings shows an example of a Box OfficeMovies listing screen 100. Within each Box Office listing screen asection 101 of the screen area is dedicated to a video or still imageused to promote PPV programming. This promotion can continue whilst thesubscriber is browsing through the listings or booking a PPV event. Thevideo or still image on the section 101 is switchable according to whichtitle is selected from a menu 102 of programmes in the lower half of thescreen 100. In FIG. 7 the bar 103 for the movie “Die Hard II” ishighlighted and a video or still image representing that movie would bedisplayed in the section 101. Thus, as the subscriber browses throughthe Box Office listings the video/still inset will change to denote theprogramme selected-the video/still being a trailer or promotion for theparticular title.

In order to reduce bandwidth any video image is transmitted at a reducedsize and is scaled up to the required size by the set top box asdescribed in our aforementioned patent applications.

As a further advancement the video or still image is itself schedulable.This enables the high bandwidth required for video promotions to be usedto greatest effect. For example, during the daytime PPV titles targetedat families and children may be scheduled for video promotions. However,in peak viewing time stills may be used to promote these events, and thevideo promotions allocated to titles appealing to a more matureaudience.

Other areas 104,105 of the screen 100 are given over to the display of acompany and/or channel banner and text which may change depending onwhich movie is highlighted in the menu 102. Icons 106 to 109 below themenu 102 enable the user to select movie listings by movie type, e. g.“Western” movies, “Action “movies”, “Comedy” movies or “Classic” movies.Selection of one of the icons 106 to 109 causes the EPG to apply theaforementioned filtering to the movie information before it is displayedon the screen 100.

Having thus described the present invention by reference to a preferredembodiment it is to be well understood that the embodiment in questionis exemplary only and that modifications and variations such as willoccur to those possessed of appropriate knowledge and skills may be madewithout departure from the spirit and scope of the invention as setforth in the appended claims and equivalents thereof.

1. A receiver for receiving television signals in a plurality ofchannels each defining a television programme and/or other servicesprovided by a broadcaster, and a channel set identity and a channelsubset identity for the channel, the receiver comprising means forstoring a reference channel set identity and one or more referencechannel subset identities, means for comparing the channel identity andchannel subset identity for a channel in a received signal with thereference channel and channel subset identities and means for outputtingthe received television signal for display of the programme or otherservices defined thereby depending on the comparison.
 2. A receiver asclaimed in claim 1, wherein the storing means is arranged to store acommon channel subset identifying programmes and/or other servicesreceivable independent of the receivers location and a regional channelsubset identifying programmes and/or other services receivable dependingon the location of the receiver.
 3. A receiver as claimed in claim 1,wherein each channel has associated with it a logical channel numberwhich varies on a channel subset basis, the receiver comprising meansfor displaying a list of programmes and/or other services containing thelogical channel number.
 4. A receiver as claimed in claim 1, whereineach channel has associated with it an order channel number which varieson a channel subset basis, the receiver comprising means for displayinga list of programmes and/or other services depending the order channelnumber.
 5. A receiver as claimed in claim 1, wherein each channel hasassociated with it one or more indicators, the receiver comprising meansresponsive to the indicators for controlling display of programme and/orservice information.
 6. A receiver as claimed in claim 2, wherein eachchannel has associated with it a logical channel number which varies ona channel subset basis, the receiver comprising means for displaying alist of programmes and/or other services containing the logical channelnumber.
 7. A receiver as claimed in claim 2, wherein each channel hasassociated with it an order channel number which varies on a channelsubset basis, the receiver comprising means for displaying a list ofprogrammes and/or other services depending the order channel number. 8.A receiver as claimed in claim 3, wherein each channel has associatedwith it an order channel number which varies on a channel subset basis,the receiver comprising means for displaying a list of programmes and/orother services depending the order channel number.
 9. A receiver asclaimed in claim 6, wherein each channel has associated with it an orderchannel number which varies on a channel subset basis, the receivercomprising means for displaying a list of programmes and/or otherservices depending the order channel number.
 10. A receiver as claimedin claim 2, wherein each channel has associated with it one or moreindicators, the receiver comprising means responsive to the indicatorsfor controlling display of programme and/or service information.
 11. Areceiver as claimed in claim 3, wherein each channel has associated withit one or more indicators, the receiver comprising means responsive tothe indicators for controlling display of programme and/or serviceinformation.
 12. A receiver as claimed in claim 4, wherein each channelhas associated with it one or more indicators, the receiver comprisingmeans responsive to the indicators for controlling display of programmeand/or service information.
 13. A receiver as claimed in claim 6,wherein each channel has associated with it one or more indicators, thereceiver comprising means responsive to the indicators for controllingdisplay of programme and/or service information.
 14. A receiver asclaimed in claim 7, wherein each channel has associated with it one ormore indicators, the receiver comprising means responsive to theindicators for controlling display of programme and/or serviceinformation.
 15. A receiver as claimed in claim 8, wherein each channelhas associated with it one or more indicators, the receiver comprisingmeans responsive to the indicators for controlling display of programmeand/or service information.
 16. A receiver as claimed in claim 9,wherein each channel has associated with it one or more indicators, thereceiver comprising means responsive to the indicators for controllingdisplay of programme and/or service information.